The research proposed involves four interrelated areas. The first set of proposals involves a continuation of clinical studies designed to examine the role of human prolactin in problems of infertility; to define the natural history of prolactin secreting adenomas and to assess medical therapy of these pituitary tumors. The influence of endorphins on prolactin and pituitary hormone secretion is a related experimental study. The second major thrust of the research proposal focuses on prolact and growth hormone receptors. Studies on the purification, characterization, biosynthesis and degradation of receptors are to be explored in whole animals and in tissue culture studies in an attempt to gain better understanding of the mechanism of action of those two hormones. The third area to be explored is the purification and physiology of placental lactogen particularly in the rat, sheep and cow. These studies are designed to shed light on the biological role and control of secretion of placental hormones. The fourth area involves examining and identifying novel pituitary and tissue growth factors. One of these, a mammary tumor growth factor, is of particular interest because its production may be under endocrine control.